Variable-capacity compressor.



' ammo muonvrnae, or MILWAUKEE, W sconsin.

VARIABLE-CAPACITY COMPRESSOR.

I Specification of Letters Patent.

Application filed Septemher8, 1903. Serial No. 172,367. 1

To all whom it may concern. Be it known that I, BRUNO V. NORDBERG, a citizen of the United' States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in V ariable- Capacity Compressors, of which the following is a specification, reference being had to the accompanying drawing, forming a part 1'0 thereof.

.The main object of this invention is to automatically vary the volume of air c0 mpressed and discharged by a compressor running at a constant speed, according to fluctuations in the demand for compressed air or gas. 1

It consists in certain novel features of o I) l construction and in the peculiar arrangement. and combinations of parts hereinafter particularly described and pointed out in the claims.

In the accompanying drawing like characters designate the same parts in theseveral figures. a

Figure 1 is a side elevation of a. .compressor embodying the invention; Fig. 2 is "a detail view on an enlarged scale of auto .maticvalve gear for operating the exhaust or auxiliary outlet valves; Fig. 3 is a vereo-tical longitudinal section on an enlarged scale of one end of the compressor cylinder and offone set of valves, the valves being duplicated at the other end of the cylinder;

and Fig. 4 is a vertical medial section on an enlarged scale of the pressure regulator.

Heretofcre in some instances the volume of air or gas delivered by a compressor running at a constant speed has been varied either by throttling the whole volume of air before it enters the cylinder, thereby reducing its density, or by unloadin the compressor, which has been accomplis ed either- \by establishing communication between the;

interior of the cylinder and the atmosphere.

or by establishing communication between theends of thec'ylinder, thereby stopping the delivery of air altogether. The first method is objectionable because by throttling the air, the work of compression is increased .50 above that necessary to compress the same quantity of air from atmospheric pressure to the required pressure. The second method is objectionable-because the whole load of the compressor is put on or thrown off, thereby subjecting the motor, which in most cases is either an electric motor or a water wheel, to extreme variations of load, it being very difiicult, if notimpossible, to govern the tainment of the above stated object, .a is the cylinda r, Z; the piston, c one of the. automatic sucticf; valves, d one of the automatic discharge valves, and 0 one of the exhaust or auxiliary outlet valves. The suction and discharge valvesc and d are of the ordinary or any suitable type of spring seated puppet.

I Patented Dec.24;,1912.

' sor cylinder and valves suitable for the atvalves, and the outlet valves 0 are pre'ferably of the semi-rotative Corliss type. The

exhaust valves e may be operated by any full stroke automatic valve gear of theCorlisstype, such for example as is shown in United States,- Letters Patent No. 680,667,

granted to me August 13, 1901. I have shown for the purpose, and will briefly describe,

valve gear essentially like that shown and described in my former patent in principle and mode of operation, but 'slightly modified to adapt it to my present purpose.

Referring to Figs. land 2, f are the valve '6, and connected by rods 9 with the pistons closing arms fixed on the stems of thevalves I of dash pots h. z are the valve opening arms loosely mounted on the valve stems and connected by rods with a wrist lever j. is are trip ca ns ivoted to thearms i, and Z are trip arms a so pivoted tosaid armed and having crank pins engaged by said cams. m'and n are latch blocks attached to the arms 'f and 1 respectively. The wrist lever j is connected by a rod With ii. rocker arm 0, which is in turn connected by a rod and strap with an eccentric p on the crank shaft g. The trip cams k are operated, and

the times or points of closing the exhaust yalves e. withrelation tothe movements of the piston b are determined, by an automatic pressure regulator, which consists generally of a vertical cylinder 1, fixed to the compressor frame, a plunger .9 fitted in the lower end of said cylinder, a sleeve 25 fitted and movable vertically upon said cylinder, a spring u between the plunger 8 and the upper end of said sleeve, and a check or retarding device which is opposed to the iovement of said sleeve and may consist of a dash pot (2, formed in or attached to the upper end of said sleeve, and a plunger w titted in said dash pot and fixed to a stand a, which is attached to the compressor frame. The sleeve t is adjustably weighted by divided rings y, which determine the pressure to be produced and maintained by the compressor and said weighted sleeve constitutes a weight for determining said pressure. The lower end of the cylinder '1 is connected by a pipe with the discharge chest of the compressor or the compressed air reservoir. The sleeve If is connected by crank arms with a. rocker shaft '2, which is supported by the stand (/0. A T-lever 3, which is suspended by a bar l from the shaft 2, has its opposite arms connected by rods with the cams la and its intermediate arm 5 connected by a rod 6 with a corresponding arm 7 on the shaft 2. The bar 4, rod (3 and arms 5 and 7 form a jointed parallelogram, which is swung to and fro by an eccentric S on the crank shaft 9', connected by a strap and rod with a rocker arm 9, which is in turn connected by a rod with the bar 1. The eccentric 72 operates to swing the arms back and forth between constant limits, and to open the valves 6 when the piston starts on its compressing strokes, if the trip cams are in position to permit the engagement of the latch blocks; otherwise, said valves will not be opened. The eccentric 8 operates to swing the trip cams It: back and forth and to disengage the latch blocks, thus permitting the sudden closing of the valves 6 at different points in the compressing strokes of the piston according to the position of the plunger 3 of the regulator. An increase in pressure which causes said plunger to rise, produces a later closing of said valves, while a fall in pressure which allows the plunger to descend, produces an earlier closing of said valves.

The operation of the compressor as here in shown and described may be explained as follows: Assuming that the plunger .9 of the regulator ,is in a position to trip the exhaust valves .6 at the middle of the compressing strokes of'the piston, the piston during the first half of each compressing stroke,,.will discharge the air ahead of it through the open exhaust valve at the end of the cylinder toward which the piston is advancing, the suction and discharge valves As the pissame operations will take place in the opposite end of the cylinder, while at that end from which the piston is receding the discharge valve (Z and the exhaust valve 6 being closed, air will be admitted to the eyl inder behind the piston through the suction valve v. if the pressure rises in the discharge chest or reservoir. the plunger .9 of the regulator will be lit" 1 and thereby .-lll'l b the cams in so as to ease and cause the exhaust valves 0 to close later with reference to the compressing strokes of the piston, so that air will be discharged from the cylinder ahead of the piston for a greater portion of its compressing strokes, and a smaller volume will be compressed and delivered into the discharge chest. If on the other hand, the pressure falls, allowing the plungerc to descend, the valves 6 will be released and closed earlier with respect to the compressing strokes of the piston, and a greater volume of air will be en trapped in the cylinder and compressed. In this way the volume of air compressed on each stroke of the piston may be varied from zero, when the exhaust valves are not tripped and remain open to the end of the compressing strokes of the piston, up to the entire capacity of the cylinder, whenthe exhaust valves are tripped at the beginning of, and remain closed during, the entire compressing strokes of the piston, according to the demand on the compressor. The weight applied to the sleeve L of the regulator determines the discharge pressure, an increase in weight increasing suchfpressure.

The spring u, which forms arf elastic connection between the plunger-'6 and the Weighted sleeve 17, and the dash pot 'v and plunger to, which check or retard the movement of the weighted sleeve 25, prevent the trip cams is from responding to momentary fluctuations orpulsations in the discharge pressure, since the plunger 8 lifted only for an instant by a sudden and temporaryincrease of pressure, will compress the spring u and resume its original position before the weighted sleeve t has time to overcome the resistance of the dash pot 7) and plun er w; and in like manner, a momentary epression of the plunger will extend the spring for an instant without moving said sleeve; j

Various changes in details of constructhe compressor consisting of the combination with the compressor cylinder and" piston andwith suction and discharge valves, of a rotatiue exhaust valve, means for posi tively opening the exhaust valve at the beginning of the compression stroke, automatic variable valve-operating and releasing gear comprising a closing arm, an opening arm provided with a latch, and a trip cam arranged to release and close said' exhaust valve at different points in the compression stroke of the piston, and an automatic pressure regulator operated by the' discharge pressure of the compressor and connected with said cam to vary the point of closing the exhaust valve according to variations in the demand upon the compressor, substantially as described. a

2. In a variable capacity compressor, mechanism for compressing to a constant pressure. by varying the closing of an eX haust valve controlled by the demand on the compressor consisting of the combination with the compressor cylinder and piston and self'acting suction and discharge.

valves, of rotative exhaust valves at the ends of the cylinder, means for positively opening the exhaust valves at the beginning of the compression stroke, an automatic variable valve-operating and releasing gear comprising closing arms, opening arms provided with latches and trip arms operatively connected with said exhaust valves to positively release and close the same at dilferent' points in the compression strokes'of the piston, and a pressure regulator actuated by pressure from thecompressor and connected with said cams, substantially as described.

3.111 a variable capacity compressor, mechanism for compressing to a constant pressure by varying the closing of an eX- haust valve controlled by the demand on the compressorconsisting of the combination with the cylinder and piston and with suction'and' discharge valves, of an independent exhaust valve, automatic varlable valve-operating gear comprising a trip cam and arranged to close said exhaust valve at different points in the compression stroke of the piston, and an automatic pressure regulator consisting of a pressure cylindenand a ,pluuger'fitted in said cylindcrand connected with the trip cam through the me dium of means com rising a spring, a pressure controlling weight and retarding dea cylinder and piston, of inlet and outlet 1 valves and independent exhaust valves, automatic valve. gear including tripping mechanism arranged to actuate the said valves to vary the volume of air or gas compressed, and a pressure regulator for effecting a constant pressure comprising a eight and connection between it and tripping mechanism for said valve'gear, and a retarding device co-acting with said pressure regulator, sub-' stantially as described. H

5. In a variable capacity compressor, mechanism for-"compressing to a constant pressure by varying the closing of anexhaust valve controlled by the demand on the compressor consisting of the combination with the compressor cylinder and piston, of inlet and outlet valves, automatic valve gear arranged to vary the volume of air or gas compressed by said piston in said cylinder, and an automatic pressure regulator comprising a weight and connections between it and the tripping mechanism ofsaid valve gear, an expansion chamber connected with a source of pressure and pr0- vided with a movable part having an elastic connection with said weight, and a check ing device opposed to the movement of said weight, said pressure regulator bemg'controlled by pressure from the compressor, spbstantially as described. In a variable capacity compressor, methanism for compressing to a constant pressure by varying the closing of an ex haust valve controlled by the demand on the compressor consisting of the combination with the compressor cylinder having a pis- .ton and inlet, and outlet valves, of automatic valvege'ar adapted to vary the volume of air or gas compressed and an automatic pressure regulator comprising an ad justable weight and connections between it and the tripping mechanism of saidvalve gear, an expansion chamber having a movable part, and a spring connection between said part and Weight, said pressure regu-' lator being controlled by pressure from the cpmpressor, substantially as described.

In a variable capacity compressor,

mechanism for compressing to a constant pressure by varying the closing of an exhaust valve controlledby the demand .on the compressor consisting of the combination,

'with the compressor cylinder having .a pis- .ton-and inlet and outletvalves, of automatic valve gear adapted to vary the volume of & 1,047,977

air or gas euinpressed, and an automatic beingeontrolled by pressure from the comregulator comprising a Weight and c0nneepressor, substantially as described. 1O tions between it and the tripping mecha- In Witness whereof, 1 hereto aflix my signism of said valve gear, an expansion cliamnature in presence of two Witnesses.

her having a movable part, a spring connee- BRUNO V. NORDBERG.

tion between saidv part and Weight, and a Witnesses:

fluid checking device opposed to the move- CHAS. L. Gross ment of said weight, said pressure regulator ALICE E. Goss. 

